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Abstract:

An access point terminal includes: a communication-terminal-status
determination unit which determines a communication status of one
wireless communication terminal out of wireless communication terminals,
by obtaining a wireless signal transmitted or received by the one
wireless communication terminal; and a frequency control unit which uses
(i) a first frequency band for wireless communication with the one
wireless communication terminal and (ii) a frequency band other than the
first frequency band for the wireless communication with one or more of
the wireless communication terminals other than the one wireless
communication terminal, when the communication-terminal-status
determination unit determines that the communication status of the one
wireless communication terminal satisfies a predetermined condition.

Claims:

1. An access point terminal which performs wireless communication with
each of a plurality of wireless communication terminals, using one of a
plurality of frequency bands, said access point terminal comprising: a
communication-terminal-status determination unit configured to determine
a communication status of one wireless communication terminal out of the
wireless communication terminals, by obtaining a wireless signal
transmitted or received by the one wireless communication terminal; and a
frequency control unit configured to use (i) a first frequency band for
the wireless communication with the one wireless communication terminal
and (ii) a frequency band other than the first frequency band for the
wireless communication with one or more of the wireless communication
terminals other than the one wireless communication terminal, when said
communication-terminal-status determination unit determines that the
communication status of the one wireless communication terminal satisfies
a predetermined condition.

2. The access point terminal according to claim 1, further comprising an
SSID issuance management unit configured to assign an SSID to each of the
wireless communication terminals requesting a start of wireless
communication, the SSID being unique to each of the wireless
communication terminals.

3. The access point terminal according to claim 1, further comprising an
SSID issuance management unit configured to assign an SSID to each of the
wireless communication terminals requesting a start of wireless
communication, the SSID being unique to each of categories to which the
wireless communication terminals belong.

4. The access point terminal according to claim 1, further comprising a
communication terminal management unit configured to hold, for each of
the wireless communication terminals, (i) the SSID assigned to the
wireless communication terminal and (ii) a channel in a frequency band
currently being used for the wireless communication with the wireless
communication terminal, such that the SSID and the channel are associated
with each other, wherein said frequency control unit is configured to
switch between frequency bands to be used in the wireless communication
with the wireless communication terminal, by changing the association
between the SSID and the channel held in said communication terminal
management unit.

5. The access point terminal according to claim 4, wherein said
communication terminal management unit is further configured to hold, for
each of the wireless communication terminals, a frequency band which has
been used immediately before the frequency band currently being used, and
when said communication-terminal-status determination unit determines
that the communication status of the one wireless communication terminal
has changed from a status that satisfies the predetermined condition to a
status that does not satisfy the predetermined condition, said frequency
control unit is configured to switch, to the first frequency band, a
frequency band of a wireless communication terminal which is (i)
currently using the frequency band other than the first frequency band
and (ii) has used the first frequency band immediately before, the
wireless communication terminal being included in the wireless
communication terminals managed by said communication terminal management
unit.

6. The access point terminal according to claim 1, wherein said
communication-terminal-status determination unit is configured to
determine, as the communication status, a traffic volume of a wireless
signal transmitted or received by each of the wireless communication
terminals that belong to a specific category that requires
real-timeliness in the wireless communication, and when the
communication-terminal-status determination unit determines that the
traffic volume of the wireless signal transmitted or received by one of
the wireless communication terminals that belong to the specific category
is greater than a predetermined threshold, said frequency control unit is
configured to use (i) the first frequency band for the wireless
communication with the wireless communication terminals that belong to
the specific category, and (ii) the frequency band other than the first
frequency band for the wireless communication with the wireless
communication terminal other than the wireless communication terminals
that belong to the specific category.

7. The access point terminal according to claim 1, wherein each of the
wireless communication terminals transmits and receives the wireless
signal that includes information indicating a priority of the wireless
signal, said communication-terminal-status determination unit is
configured to determine, as the communication status, the priority of the
wireless signal transmitted or received by each of the wireless
communication terminals that belong to the specific category that
requires real-timeliness in the wireless communication, and when the
communication-terminal-status determination unit determines that the
priority of the wireless signal transmitted or received by one of the
wireless communication terminals that belong to the specific category is
greater than a predetermined threshold, said frequency control unit is
configured to use (i) the first frequency band for wireless communication
with the wireless communication terminals that belong to the specific
category and (ii) the frequency band other than the first frequency band
for the wireless communication with one or more of the wireless
communication terminals other than the wireless communication terminals
that belong to the specific category.

8. The access point terminal according to claim 1, wherein said
communication-terminal-status determination unit is configured to
determine that the communication status of the one wireless communication
terminal satisfies the predetermined condition, when an application
execution notification is received from the one wireless communication
terminal, the application execution notification indicating that
execution of an application requiring the real-timeliness higher than a
predetermined value in the wireless communication has started.

9. The access point terminal according to claim 5, wherein said
communication-terminal-status determination unit is configured to
determine that the communication status of the one wireless communication
terminal has changed from a status that satisfies the predetermined
condition to a status that does not satisfy the predetermined condition,
when an application completion notification is received from the one
wireless communication terminal, the application completion notification
indicating that the execution of the application requiring the
real-timeliness higher than the predetermined value in wireless
communication is completed.

10. A wireless communication terminal which is one wireless communication
terminal out of a plurality of wireless communication terminals which
perform wireless communication with an access point terminal using one of
a plurality of frequency bands, said wireless communication terminal
comprising: an application control unit configured to execute an
application which requires wireless communication with said access point
terminal; an application determination unit configured to determine
real-timeliness in the wireless communication required for the
application executed by said application control unit; and an application
information notification unit configured to, when the real-timelimess
determined by said application determination unit is greater than a
predetermined threshold, cause said access point terminal to use (i) a
first frequency band for wireless communication with the one wireless
communication terminal and (ii) a frequency band other than the first
frequency band for wireless communication with one or more of the
wireless communication terminals other than the one wireless
communication terminal, by transmitting an application execution
notification to said access point terminal.

11. The wireless communication terminal according to claim 10, wherein,
when the execution of the application that has been executed by said
application control unit is completed, said application information
notification unit is further configured to cause the access point
terminal to return a frequency band of a wireless communication terminal
that has had the frequency band switched according to the application
execution notification back to the frequency band used prior to the
switching, out of the wireless communication terminals, by transmitting
an application completion notification to the access point terminal.

12. A wireless communication system comprising a plurality of wireless
communication terminals and an access point terminal which perform
wireless communication using one of a plurality of frequency bands,
wherein one wireless-communication terminal out of said wireless
communication terminals includes: an application control unit configured
to execute an application which requires the wireless communication with
said access point terminal; an application determination unit configured
to determine real-timeliness in the wireless communication required for
the application executed by said application control unit; and an
application information notification unit configured to transmit an
application execution notification to said access point terminal, when
the real-timelimess determined by said application determination unit is
greater than the predetermined threshold, and said access point terminal
including: a communication-terminal-status determination unit configured
to determine a communication status of said one wireless communication
terminal, by receiving the application execution notification; and a
frequency control unit configured to use (i) a first frequency band for
the wireless communication with said one wireless communication terminal
and (ii) a frequency band other than the first frequency band for the
wireless communication with one or more of said wireless communication
terminals other than the one wireless communication terminal, when said
communication-terminal-status determination unit determines that the
communication status of said one wireless communication terminal
satisfies a predetermined condition.

13. A method of performing wireless communication with each of a
plurality of wireless communication terminals, using one of a plurality
of frequency bands, said method comprising: determining a communication
status of one wireless communication terminal out of the wireless
communication terminals, by obtaining a wireless signal transmitted or
received by the one wireless communication terminal; and using (i) a
first frequency band for the wireless communication with the one wireless
communication terminal and (ii) a frequency band other than the first
frequency band for the wireless communication with one or more of the
wireless communication terminals other than the one wireless
communication terminal, when it is determined in said determining that
the communication status of the one wireless communication terminal
satisfies a predetermined condition.

14. A method of performing wireless communication performed by one
wireless communication terminal out of a plurality of wireless
communication terminals which perform the wireless communication with an
access point terminal, using one of a plurality of frequency bands, said
method comprising: executing an application which requires the wireless
communication with the access point terminal; determining real-timeliness
in the wireless communication required for the application executed in
said executing; and causing, when the real-timelimess determined in said
determining is greater than a predetermined threshold, the access point
terminal to use (i) a first frequency band for wireless communication
with the one wireless communication terminal, and (ii) a frequency band
other than the first frequency band for the wireless communication with
one or more of the wireless communication terminals other than the one
wireless communication terminal, by transmitting an application execution
notification to the access point terminal.

15. A non-transitory computer-readable recording medium for use in a
computer and on which a program is recorded, the program being for
causing the computer to perform wireless communication with each of a
plurality of wireless communication terminals, using one of a plurality
of frequency bands, and the program causing the computer to execute:
determining a communication status of one wireless communication terminal
out of the wireless communication terminals, by obtaining a wireless
signal transmitted or received by the one wireless communication
terminal; and using (i) a first frequency band for the wireless
communication with the one wireless communication terminal and (ii) a
frequency band other than the first frequency band for the wireless
communication with one or more of the wireless communication terminals
other than the one wireless communication terminal, when it is determined
in said determining that the communication status of the one wireless
communication terminal satisfies a predetermined condition.

16. A non-transitory computer-readable recording medium for use in a
computer and on which a program is recorded, the program being for
causing one wireless communication terminal out of a plurality of
wireless communication terminals which perform wireless communication
with an access point terminal to perform the wireless communication with
the access point terminal, using one of a plurality of frequency bands,
and the program causing the one wireless communication terminal to
execute: executing an application which requires the wireless
communication with the access point terminal; determining real-timeliness
in the wireless communication to required for the application executed in
said executing; and causing, when it is determined in said determining
that the real-timelimess is greater than the predetermined threshold, the
access point terminal to use (i) a first frequency band for the wireless
communication with the one wireless communication terminal, and (ii) a
frequency band other than the first frequency band for the wireless
communication with one or more of the wireless communication terminals
other than the one wireless communication terminal, by transmitting an
application execution notification to said access point terminal.

17. An integrated circuit which performs wireless communication with each
of a plurality of wireless communication terminals, using one of a
plurality of frequency bands, said integrated circuit comprising: a
communication-terminal-status determination unit configured to determine
a communication status of one wireless communication terminal out of the
wireless communication terminals, by obtaining a wireless signal
transmitted or received by the one wireless communication terminal; and a
frequency control unit configured to use (i) a first frequency band for
the wireless communication with the one wireless communication terminal
and (ii) a frequency band other than the first frequency band for the
wireless communication with one or more of the wireless communication
terminals other than the one wireless communication terminal, when said
communication-terminal-status determination unit determines that the
communication status of the one wireless communication terminal satisfies
a predetermined condition.

18. An integrated circuit which is provided on one wireless communication
terminal out of a plurality of wireless communication terminals which
perform wireless communication with an access point terminal, using one
of a plurality of frequency bands, said integrated circuit comprising: an
application control unit configured to execute an application which
requires the wireless communication with the access point terminal; an
application determination unit configured to determine real-timeliness in
the wireless communication required for the application executed by said
application control unit; and an application information notification
unit configured to, when the real-timelimess determined by said
application determination unit is greater than the predetermined
threshold; cause the access point terminal (i) to use a first frequency
band for the wireless communication with the one wireless communication
terminal, and (ii) to use a frequency band other than the first frequency
band for the wireless communication with one or more of the wireless
communication terminals other than the one wireless communication
terminal, by transmitting an application execution notification to the
access point terminal.

Description:

CROSS REFERENCE TO RELATED APPLICATION(S)

[0001] This is a continuation application of PCT Patent Application No.
PCT/JP2011/003531 filed on Jun. 21, 2011, designating the United States
of America, which is based on and claims priority of Japanese Patent
Application No. 2010-141045 filed on Jun. 21, 2010. The entire
disclosures of the above-identified applications, including the
specifications, drawings and claims are incorporated herein by reference
in their entirety.

BACKGROUND OF THE INVENTION

[0002] (1) Field of the Invention

[0003] The present invention relates to information processing techniques,
and particularly to an information processing technique that enables
efficient use of a band in wireless communication.

[0004] (2) Description of the Related Art

[0005] In recent years, many devices which can be used with wireless LANs
are commercialized and it is possible to use various applications with
ease and convenience. Furthermore, it is known that the advent of
Institute of Electrical and Electronics Engineers (IEEE) 802.11n has
allowed a faster and more stable wireless communication, and thus, for
example, streaming of a high-image-quality video can be performed at home
using Digital Living Network Alliance (DLNA).

[0006] However, as the number of wireless LAN devices increases, there are
cases where a user cannot execute a service smoothly because a band
available for a wireless LAN device is overwhelmed. Furthermore, in a 2.4
GHz band, there is a problem that radio wave interference frequently
occurs when the band is used by various devices, because the 2.4 GHz band
is an Industry Science Medical (ISM) band.

[0007] Therefore, in general, a 5 GHz band with less interference is used
for a wireless signal that requires high real-timeliness, such as that
for video. In contrast, the 2.4 GHz band is sufficient for use in content
downloading or web browsing. However, if all terminals are connected
through the 5 GHz band as there is less interference, the 5 GHz band
becomes overwhelmed, which is like putting the cart before the horse.
Therefore, it is preferable to determine which of the 2.4 GHz band and
the 5 GHz band to use, depending on the level of real-timeliness required
for the wireless communication.

[0008] As a technique for using such wireless bands efficiently, there is
known a line acquisition method for a wireless IP phone service using a
wireless LAN that controls the wireless band, by (i) controlling wireless
IP phones connected to SSIDs in an integrated manner as shown in FIG. 25
and (ii) restricting a communication traffic volume to be equal to or
less than a threshold set for SSIDs of an access point terminal (see
Patent Literature 1: Japanese Unexamined Patent Application Publication
No. 2007-214657).

[0009] However, with the effective usage of wireless LAN band in the line
acquisition method having the configuration described above, the
communication traffic volume per se is restricted equally for all of the
terminals. Therefore, a band is unnecessarily allocated to a terminal
which is not requiring a band, which makes it impossible to properly
allocate a band for a terminal which is requiring a band. Furthermore,
restricting a communication traffic volume is not always effective, since
in general a wireless band cannot be quantitatively manipulated.

[0010] The present invention has been conceived in view of the
above-described conventional problems and aims to provide an access point
terminal capable of improving an efficiency in use of the wireless band,
by moving a terminal to an appropriate operating frequency without
controlling the communication traffic volume.

SUMMARY OF THE INVENTION

[0011] An access point terminal according to an aspect of the present
invention performs wireless communication with each of a plurality of
wireless communication terminals, using one of a plurality of frequency
bands. Specifically, the access point terminal includes: a
communication-terminal-status determination unit which determines a
communication status of one wireless communication terminal out of the
wireless communication terminals, by obtaining a wireless signal
transmitted or received by the one wireless communication terminal; and a
frequency control unit which uses (i) a first frequency band for the
wireless communication with the one wireless communication terminal and
(ii) a frequency band other than the first frequency band for the
wireless communication with one or more of the wireless communication
terminals other than the one wireless communication terminal, when the
communication-terminal-status determination unit determines that the
communication status of the one wireless communication terminal satisfies
a predetermined condition.

[0012] The above configuration allows, for example, to allocate (i) the
first frequency band to the one wireless communication terminal requiring
high real-timeliness in the wireless communication and (ii) the frequency
band other than the first frequency band to other terminals, which
enables a proper and efficient allocation of the frequency bands
depending on the intended use.

[0013] As an aspect, the access point terminal may further include an SSID
issuance management unit which assigns an SSID to each of the wireless
communication terminals requesting a start of wireless communication, the
SSID being unique to each of the wireless communication terminals. This
allows the one wireless communication terminal to occupy the first
frequency band when a communication status satisfies the predetermined
condition.

[0014] As another aspect, the access point terminal may further include an
SSID issuance management unit which assigns an SSID to each of the
wireless communication terminals requesting a start of wireless
communication, the SSID being unique to each of categories to which the
wireless communication terminals belong. This allows all of the wireless
communication terminals that belong to a specific category to communicate
wirelessly using the first frequency band.

[0015] The access point terminal may further include a communication
terminal management unit which holds, for each of the wireless
communication terminals, (i) the SSID assigned to the wireless
communication terminal and (ii) a channel in a frequency band currently
being used for the wireless communication with the wireless communication
terminal, such that the SSID and the channel are associated with each
other. The frequency control unit may switch between frequency bands to
be used in the wireless communication with the wireless communication
terminal, by changing the association between the SSID and the channel
held in the communication terminal management unit.

[0016] The communication terminal management unit may further hold, for
each of the wireless communication terminals, a frequency band which has
been used immediately before the frequency band currently being used.
When the communication-terminal-status determination unit determines that
the communication status of the one wireless communication terminal has
changed from a status that satisfies the predetermined condition to a
status that does not satisfy the predetermined condition, the frequency
control unit may switch, to the first frequency band, a frequency band of
a wireless communication terminal which is (i) currently using the
frequency band other than the first frequency band and (ii) has used the
first frequency band immediately before, the wireless communication
terminal being included in the wireless communication terminals managed
by the communication terminal management unit.

[0017] As an aspect, the communication-terminal-status determination unit
may determine, as the communication status, a traffic volume of a
wireless signal transmitted or received by each of the wireless
communication terminals that belong to a specific category that requires
real-timeliness in the wireless communication. When the
communication-terminal-status determination unit determines that the
traffic volume of the wireless signal transmitted or received by one of
the wireless communication terminals that belong to the specific category
is greater than a predetermined threshold, the frequency control unit may
use (i) the first frequency band for the wireless communication with the
wireless communication terminals that belong to the specific category,
and (ii) the frequency band other than the first frequency band for the
wireless communication with the wireless communication terminal other
than the wireless communication terminals that belong to the specific
category.

[0018] As another aspect, when each of the wireless communication
terminals transmits and receives the wireless signal that includes
information indicating a priority of the wireless signal, the
communication-terminal-status determination unit may determine, as the
communication status, the priority of the wireless signal transmitted or
received by each of the wireless communication terminals that belong to
the specific category that requires real-timeliness in the wireless
communication. When the communication-terminal-status determination unit
determines that the priority of the wireless signal transmitted or
received by one of the wireless communication terminals that belong to
the specific category is greater than a predetermined threshold, the
frequency control unit may use (i) the first frequency band for wireless
communication with the wireless communication terminals that belong to
the specific category and (ii) the frequency band other than the first
frequency band for the wireless communication with one or more of the
wireless communication terminals other than the wireless communication
terminals that belong to the specific category.

[0019] Furthermore, the communication-terminal-status determination unit
may determine that the communication status of the one wireless
communication terminal satisfies the predetermined condition, when an
application execution notification is received from the one wireless
communication terminal, the application execution notification indicating
that execution of an application requiring the real-timeliness higher
than a predetermined value in the wireless communication has started.

[0020] Moreover, the communication-terminal-status determination unit may
determine that the communication status of the one wireless communication
terminal has changed from a status that satisfies the predetermined
condition to a status that does not satisfy the predetermined condition,
when an application completion notification is received from the one
wireless communication terminal, the application completion notification
indicating that the execution of the application requiring the
real-timeliness higher than the predetermined value in wireless
communication is completed.

[0021] The wireless communication terminal according to an aspect of the
present invention is one wireless communication terminal out of a
plurality of wireless communication terminals which perform wireless
communication with an access point terminal using one of a plurality of
frequency bands. Specifically, the wireless communication terminal
includes: an application control unit which executes an application which
requires wireless communication with the access point terminal; an
application determination unit which determines real-timeliness in the
wireless communication required for the application executed by the
application control unit; and an application information notification
unit which causes, when the real-timelimess determined by the application
determination unit is greater than a predetermined threshold, the access
point terminal to use (i) a first frequency band for wireless
communication with the one wireless communication terminal and (ii) a
frequency band other than the first frequency band for wireless
communication with one or more of the wireless communication terminals
other than the one wireless communication terminal, by transmitting an
application execution notification to the access point terminal.

[0022] The above configuration allows to allocate (i) the first frequency
band to a wireless communication terminal, at a time when the application
requiring high real-timeliness in the wireless communication is executed,
and (ii) frequency bands other than the first frequency band to other
terminals, which enables a proper and efficient allocation of the
frequency bands depending on the intended use.

[0023] Furthermore, when the execution of the application that has been
executed by the application control unit is completed, the application
information notification unit may further cause the access point terminal
to return a frequency band of a wireless communication terminal that has
had the frequency band switched according to the application execution
notification back to the frequency band used prior to the switching, out
of the wireless communication terminals, by transmitting an application
completion notification to the access point terminal.

[0024] The wireless communication system according to an aspect of the
present invention includes a plurality of wireless communication
terminals and an access point terminal which perform wireless
communication using one of a plurality of frequency bands. One wireless
communication terminal out of the wireless communication terminals
includes: an application control unit which executes an application which
requires the wireless communication with the access point terminal; an
application determination unit which determines real-timeliness in the
wireless communication required for the application executed by the
application control unit; and an application information notification
unit which transmits an application execution notification to the access
point terminal, when the real-timelimess determined by the application
determination unit greater than the predetermined threshold. The access
point terminal includes: a communication-terminal-status determination
unit which determines a communication status of the one wireless
communication terminal, by receiving the application execution
notification; and a frequency control unit which uses (i) a first
frequency band for the wireless communication with the one wireless
communication terminal and (ii) a frequency band other than the first
frequency band for the wireless communication with one or more of the
wireless communication terminals other than the one wireless
communication terminal, when the communication-terminal-status
determination unit determines that the communication status of the one
wireless communication terminal satisfies a predetermined condition.

[0025] A method of wireless communication according to an aspect of the
present invention is a method of performing wireless communication with
each of a plurality of wireless communication terminals, using one of a
plurality of frequency bands. Specifically, the method includes:
determining a communication status of one wireless communication terminal
out of the wireless communication terminals, by obtaining a wireless
signal transmitted or received by the one wireless communication
terminal; and using (i) a first frequency band for the wireless
communication with the one wireless communication terminal and (ii) a
frequency band other than the first frequency band for the wireless
communication with one or more of the wireless communication terminals
other than the one wireless communication terminal, when it is determined
in the determining that the communication status of the one wireless
communication terminal satisfies a predetermined condition.

[0026] A method of wireless communication according to other aspects of
the present invention is performed by one wireless communication terminal
out of a plurality of wireless communication terminals which perform the
wireless communication with an access point terminal, using one of a
plurality of frequency bands. Specifically, the method includes:
executing an application which requires the wireless communication with
the access point terminal; determining real-timeliness in the wireless
communication required for the application executed in the executing; and
using (i) a first frequency band for the wireless communication with the
one wireless communication terminal and (ii) a frequency band other than
the first frequency band for the wireless communication with one or more
of the wireless communication terminals other than the one wireless
communication terminal, when it is determined in the determining that the
communication status of the one wireless communication terminal is
greater than a predetermined threshold.

[0027] A non-transitory computer-readable recording medium for use in a
computer according to an aspect of the present invention is recorded with
a program for causing the computer to perform wireless communication with
each of a plurality of wireless communication terminals, using one of a
plurality of frequency bands. Specifically, the program causes the
computer to execute: determining a communication status of one wireless
communication terminal out of the wireless communication terminals, by
obtaining a wireless signal transmitted or received by the one wireless
communication terminal; using (i) a first frequency band for the wireless
communication with the one wireless communication terminal and (ii) a
frequency band other than the first frequency band for the wireless
communication with one or more of the wireless communication terminals
other than the one wireless communication terminal, when it is determined
in the determining that the communication status of the one wireless
communication terminal satisfies a predetermined condition.

[0028] A non-transitory computer-readable recording medium for use in a
computer according to other aspects of the present invention is recorded
with a program for causing one wireless communication terminal out of a
plurality of wireless communication terminals which perform wireless
communication with an access point terminal to perform the wireless
communication with the access point terminal, using one of a plurality of
frequency bands. Specifically, the program causes the one wireless
communication terminal to execute: executing an application which
requires the wireless communication with the access point terminal;
determining real-timeliness in the wireless communication required for
the application executed in the executing; and causing, when it is
determined in the determining that the real-timelimess is greater than
the predetermined threshold, the access point terminal to use (i) a first
frequency band for the wireless communication with the one wireless
communication terminal, and (ii) a frequency band other than the first
frequency band for the wireless communication with one or more of the
wireless communication terminals other than the one wireless
communication terminal, by transmitting an application execution
notification to the access point terminal.

[0029] An integrated circuit according to an aspect of the present
invention performs wireless communication with each of a plurality of
wireless communication terminals, using one of a plurality of frequency
bands. Specifically, the integrated circuit includes: a
communication-terminal-status determination unit which determines a
communication status of one wireless communication terminal out of, the
wireless communication terminals, by obtaining a wireless signal
transmitted or received by the one wireless communication terminal; and a
frequency control unit which uses (i) a first frequency band for the
wireless communication with the one wireless communication terminal and
(ii) a frequency band other than the first frequency band for the
wireless communication with one or more of the wireless communication
terminals other than the one wireless communication terminal, when the
communication-terminal-status determination unit determines that the
communication status of the one wireless communication terminal satisfies
a predetermined condition.

[0030] An integrated circuit according to other aspects of the present
invention is provided on one wireless communication terminal out of a
plurality of wireless communication terminals which perform wireless
communication with an access point terminal, using one of a plurality of
frequency bands. Specifically, the integrated circuit includes: an
application control unit which executes an application which requires the
wireless communication with the access point terminal; an application
determination unit which determines real-timeliness in the wireless
communication required for the application executed by the application
control unit; and an application information notification unit which
causes, when the real-timelimess determined by the application
determination unit is greater than the predetermined threshold, the
access point terminal (i) to use a first frequency band for the wireless
communication with the one wireless communication terminal, and (ii) to
use a frequency band other than the first frequency band for the wireless
communication with one or more of the wireless communication terminals
other than the one wireless communication terminal, by transmitting an
application execution notification to the access point terminal.

[0031] The present invention enables, for example, to (i) focus on a
wireless communication terminal which executes an application requiring
high real-timeliness in wireless communication, and (ii) allocate a first
frequency band with less radio wave interference (for example, the 5 GHz
band) to the wireless communication terminal, thereby provide a wireless
LAN environment appropriate for the usage of the wireless communication
terminal.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] These and other objects, advantages and features of the invention
will become apparent from the following description thereof taken in
conjunction with the accompanying drawings that illustrate specific
embodiments of the present invention. In the Drawings:

[0033] FIG. 1 is a configuration diagram of a wireless communication
system according to a first embodiment of the present invention;

[0034] FIG. 2 is a functional block diagram of an access point terminal
according to the first embodiment of the present invention;

[0035]FIG. 3 is a flowchart of an operation of the access point terminal
according to the first embodiment of the present invention;

[0036] FIG. 4 is a sequence diagram between the access point terminal and
a wireless communication terminal in a connection information
distribution process;

[0039] FIG. 7A shows an example of a supported frequency band, included in
device information transmission signal received from each of the wireless
communication terminals;

[0040]FIG. 7B shows an example of a desired frequency band, included in
the device information transmission signal received by each of the
wireless communication terminals;

[0041]FIG. 8A shows an example of a conversion table which holds (i) a
Primary Device Type and (ii) an operation frequency, of a wireless
communication terminal, such that the Primary Device Type and the
operation frequency are associated with each other;

[0042]FIG. 8B shows an example of the operation frequency allocated to
each of the wireless communication terminals, based on the conversion
table in FIG. 8A;

[0043]FIG. 9A shows an example of a conversion table which holds (i) a
category and (ii) the operation frequency, of a wireless communication
terminal, such that the category and the operation frequency are
associated with each other;

[0044] FIG. 9B shows an example of the operation frequency allocated to
each of the wireless communication terminals, based on the conversion
table in FIG. 9A;

[0045] FIG. 10A shows an example of a communication start request signal
received by the access point terminal in a 2.4 GHz band;

[0046] FIG. 10B shows an example of the communication start request signal
received by the access point terminal in a 5 GHz band;

[0047]FIG. 11 shows an example of the communication start request signal
for each of the frequency bands and a received power of each
communication start request signal;

[0048]FIG. 12 shows an example of the communication start request signal
and an interference state for each of the frequency bands;

[0049] FIG. 13 shows an example of communication terminal information held
by the access point terminal according to the first embodiment of the
present invention;

[0050] FIG. 14 is a flowchart showing a change of the SSID of the access
point terminal according to the first embodiment of the present
invention;

[0051]FIG. 15 shows an example of the communication terminal information
after the transfer of SSID held by the access point terminal according to
the first embodiment of the present invention is moved;

[0052]FIG. 16 shows an example of the communication terminal information
held by the access point terminal according to an second embodiment of
the present invention;

[0053]FIG. 17 is a flowchart showing a change of the SSID of the access
point terminal according to the second embodiment of the present
invention;

[0054] FIG. 18 shows an example of the communication terminal information
after the transfer of the SSID, held by the access point terminal
according to the second embodiment of the present invention;

[0056] FIG. 20 is a flowchart showing a change of the SSID of the access
point terminal according to an third embodiment of the present invention;

[0057] FIG. 21 is a flowchart showing a change of the SSID of the access
point terminal according to an fourth embodiment of the present
invention;

[0058] FIG. 22 is a functional block diagram of the access point terminal
according to an fifth embodiment of the present invention;

[0059]FIG. 23 is a flowchart showing an operation of the access point
terminal according to the fifth embodiment of the present invention;

[0060]FIG. 24 is a flowchart showing a change of the SSID of the access
point terminal according to the fifth embodiment of the present
invention; and

[0061] FIG. 25 shows a conventional technique.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0062] Embodiments of the present invention are described below with
reference to drawings.

First Embodiment

[0063] First, a configuration diagram of a wireless LAN system according
to a first embodiment is described. The wireless LAN system according to
the first embodiment includes an access point terminal 1 (hereinafter
referred to as AP) and wireless communication terminals 2 to 5
(hereinafter referred to as STA). The STA2 to the STA5 are connected
using an infrastructure mode and communicate under a control of the AP1.
The number of the STAs is 4 in the first embodiment, however, it goes
without saying that it is not limited to the number.

[0064] Furthermore, the STA2 to the STA5 are connected with the AP1 using
Wi-Fi Protected Setup (WPS), which is an easy setup for wireless LAN
advocated by Wi-Fi Alliance (WFA). It goes without saying that, without
being limited to WPS, other easy connections for wireless LAN may be
used, such as the easy connection which (i) enables an automatic key
exchange between the AP1 and each of the STA2 to the STA5, and (ii)
allows the AP1 to distribute connection information to the STA2 to the
STA5.

[0065] Furthermore, it is assumed that the AP1 is a device which is
capable of concurrently operating in frequency bands (for example, in the
2.4 GHz band and the 5 GHz band). Furthermore; although the 2.4 GHz band
and the 5 GHz band include channels, it is assumed that the AP1 according
to this embodiment performs (i) wireless communication in the 2.4 GHz
band through a channel 1 (1ch) and (ii) the wireless communication in the
5 GHz band through a channel 36 (36ch). Furthermore, the STA2 to the STA4
are devices capable of (i) selecting one of the 2.4 GHz band and the 5
GHz band and (ii) connecting to a channel in a frequency band in which
the AP1 is operating. Meanwhile, the STA5 is assumed to be a device which
operates only in the 2.4 GHz band.

[0066] When WPS is performed between the AP1, the STA2 to the STA4 are
connected with the AP1 in the 5 GHz band that is with less interference.
The STA5 is connected with the AP1 in the 2.4 GHz band, because the STA5
does not support the 5 GHz band.

[0067] The STA2 to the STA5 communicate under the control of the AP1, and
are capable of executing various applications. For example, the STA2 to
the STA5 are capable of (i) executing services from the Internet via the
AP1 and (ii) executing applications such as DLNA among the STAs.

[0068] Next, the configuration of the AP1 is described with reference to
FIG. 2.

[0070] The wireless communication interface 11 is an interface for
transmitting and receiving a wireless signal between the wireless
communication terminals. That is, the wireless communication interface 11
transmits, as a wireless signal, data generated by the
device-information-exchange control unit 10, the connection information
distribution unit 12, or the like, to each of the STA2 to the STA5.
Furthermore, the wireless communication interface 11 generates data from
a wireless signal received from the STA2 to the STA5, and notifies the
generated data to the communication-terminal-status determination unit 6,
the device-information-exchange control unit 10, or the like.
Furthermore, the wireless communication interface 11 measures a received
power of the received wireless signal, or a reception state, such as an
interference state, of each of the frequency bands. Moreover, the
wireless communication interface 11 transmits, in a predetermined time
interval, a beacon signal to each of the wireless communication terminals
managed by the communication terminal management unit 9.

[0071] The beacon signal includes a Service Set Identifier (SSID) which is
assigned to a destination wireless communication terminal, and is
transmitted using the frequency band used for wireless communication with
the wireless communication terminal. The SSID of each of the wireless
communication terminals and the frequency band to be used by each of the
wireless communication terminals are held by the communication terminal
management unit 9.

[0072] The device-information-exchange control unit (device information
obtaining unit) 10 exchanges the device information between the wireless
communication terminals which newly request a start of the wireless
communication. That is, the device-information-exchange control unit 10
(i) transmits the device information of the AP1 to the communication
terminal which newly requests a start of the wireless communication and
(ii) obtains the device information of the communication terminal which
newly requests the start of the wireless communication.

[0073] The connection information management unit 13 holds information
required by the wireless communication terminal for performing the
wireless communication with the AP1. Specifically, the connection
information management unit 13 holds key information for coding and
decoding the wireless signal. In a description on an example below, it is
assumed that the connection information management unit 13 holds the key
information in the 5 GHz band (the first frequency band) and the key
information in the 2.4 GHz band (the frequency band other than the first
frequency band). It is to be noted that the description below is based on
an assumption that the first frequency band is the 5 GHz band and the
frequency band other than the first frequency band is the 2.4 GHz band,
however, the present invention is not limited to the above. That is, it
is sufficient when the first and the second frequency bands are frequency
bands different from each other. Typically, the first frequency band is a
frequency band which is higher than the other frequency band and with
less interference, however, the present invention is not limited to the
above. Furthermore, the frequency band may be equal to or more than
three.

[0074] The connection information distribution unit 12 transmits the
connection information (key information) held by the connection
information management unit 13 to the wireless communication terminal
which newly requests a start of the wireless communication. It is to be
noted that a method of selecting the connection information to be
transmitted is not specifically limited and, for example, the following
method may be used.

[0075] For example, the connection information distribution unit 12 may
distribute, to the wireless communication terminal, all the connection
information held by the connection information management unit 13 to
cause the wireless communication terminal to select which connection
information (that is, which frequency band) to use for the wireless
communication. Alternatively, the connection information distribution
unit 12 may transmit only the connection information associated with the
frequency band used for the WPS process. Moreover, when the obtained
device information includes information indicating one or more frequency
bands supported by the wireless communication terminal, the connection
information distribution unit 12 may transmit only the connection
information associated with single frequency band selected from the one
or more frequency bands.

[0076] The communication terminal management unit 9 holds information of
each of the wireless communication terminals performing wireless
communication between the AP1. For example, the communication terminal
management unit 9 holds (i) the SSID assigned to the wireless
communication terminal and (ii) the frequency band being used for the
wireless communication between the wireless communication terminals, such
that the SSID and the frequency band is associated with each other.
Details are described later using FIG. 13.

[0077] The SSID issuance management unit 7 assigns an SSID to the wireless
communication terminal which newly requests a start of the wireless
communication. Regarding the method of assigning the SSID, for example,
the SSID issuance management unit 7 may assign a unique SSID to (i) each
of the wireless communication terminals, (ii) each of the categories to
which the wireless communication terminals belong, or (iii) each of the
channels which the wireless communication terminals use.

[0078] The communication-terminal-status determination unit 6 determines
the communication status of each of the wireless communication terminals
by obtaining the wireless signal transmitted and received by each of the
wireless communication terminals, where the communication status includes
a volume or a quality of the communication.

[0079] As an example of the volume of the communication, the traffic
volume of the wireless signal is raised. Furthermore, as an example of
the quality of the communication, priority included in the wireless
signal, more specifically, a Type of Service (ToS) or a DiffServ Code
Point (DSCP) included in an IP header is raised.

[0080] Moreover, the communication-terminal-status determination unit 6
may determine (i) that the communication status satisfies a condition,
when an application execution notification is received, and (ii) that the
communication status has changed from a status that satisfies the
condition to a status that does not satisfy the condition, when the
application completion notification is received, where the application
execution notification indicates that the execution of the application
requiring higher real-timeliness than a predetermined value in wireless
communication has started, and the application completion notification
indicates that the execution of the application requiring the higher
real-timeliness than a predetermined value in wireless communication is
completed.

[0081] The frequency control unit 8 performs a process of switching
between the frequency bands for use in the wireless communication with
each of the wireless communication terminals, according to the
communication status and so forth. For example, when the
communication-terminal-status determination unit 6 determines that the
communication status of the wireless communication terminal satisfies a
predetermined condition, the frequency control unit 8 uses the first
frequency band for the wireless communication with the wireless
communication terminal, and uses the frequency band other than the first
frequency band for the wireless communication with other communication
terminals assigned with the SSID different from the wireless
communication terminal.

[0082] Specifically, the frequency control unit 8 is capable of switching
the frequency bands for use in the wireless communication with the
wireless communication terminal assigned with the SSID, by changing the
association between the SSID and the frequency band held by the
communication terminal management unit 9.

[0083] Next, an operation of the AP1 when the start of the wireless
communication is requested from the STA2 is described with reference to
FIGS. 3 and 4. FIG. 3 is a flowchart showing steps of a connection
information distribution process. FIG. 4 is a sequence diagram between
the AP1 and the STA2 in the connection information distribution process.
It is to be noted that the AP1 operates in the same manner as the above
when the start of the wireless communication is requested from the STA3
to the STA5.

[0084] First, the AP1 receives an instruction from a user indicating that
WPS is to be started between the STA2 (S101). Specifically, upon a press
of a button (WPS start button) provided on each of the AP1 and the STA2,
the STA2 transmits a communication start request signal (Probe Request)
to the AP1.

[0085] This is a process in which the STA2 searches the AP1, which is to
be the communication partner, and corresponds to the step 1 shown in FIG.
4. Specifically, the STA2 transmits the communication start request
signal to all of the channels in the 5 GHz band and all of the channels
in the 2.4 GHz band.

[0086] Meanwhile, the AP1 (i) receives a communication start request
signal from a channel that the AP1 uses, out of the communication start
request signals transmitted from the STA2 in the 5 GHz band, and (ii)
transmits a communication start response signal (Probe Response) to the
STA2. In the same manner, the AP1 (i) receives a communication start
request signal from a channel that the AP1 uses, out of the communication
start request signals transmitted from the STA2 in the 2.4 GHz band, and
(ii) transmits a communication start response signal to the STA2. It is
to be noted that the communication start request signal and the
communication start response signal associated with each other are
transmitted and received using the same frequency band and the same
channel.

[0087] Here, when the WPS start button provided on the AP1 has been
pressed, the AP1 transmits the communication start response signal having
a PBC flag indicating that the WPS start button is pressed. Meanwhile,
the STA2 (i) determines that the AP1 which is the source of the
communication start response signal having the PBC flag is the
communication partner, and (ii) executes the step 2 shown in FIG. 4
between the AP1.

[0088] In the step 2 shown in FIG. 4, a message complying with an
Extensible Authentication Protocol over LAN (EAPOL) is transmitted and
received between the AP1 and the STA2. Here, detailed description on the
overall EAPOL is omitted to focus on some part of the EAPOL closely
related to the present invention.

[0089] The device-information-exchange control unit 10 of the AP1 obtains
device information of the STA2 (S102), by exchanging the device
information with the STA2, the device information being required for
distributing the connection information (S102). The obtained device
information is held for each of the STA2 to the STA5 by the communication
terminal management unit 9, as shown in FIG. 13. Specifically, the STA2
(i) includes various information of the STA2 into a device information
transmission signal (M1 message) and (ii) transmits the signal to the
AP1. FIG. 5 and FIG. 6 show a data structure of the device information
transmission signal. It goes without saying that the device information
transmission signal does not necessarily be the M1 message and may be a
message transmitted from the STA.

[0090] The device information transmission signal includes, for example, a
Universally Unique Identifier (uuid) which is uniquely assigned to each
device, and a device type (Primary Device Type). The Primary Device Type
is specified, for example, as shown in FIG. 6, by a combination of (i) a
Category which includes "Computer", "Displays", "Multimedia Devices", and
so forth, and (ii) a Sub Category resulting from dividing each Category
into "Television", "Personal Video Recorder (PVR)", and so forth.

[0091] Furthermore, in this embodiment, (i) a new item ("New Field" in
FIG. 5) may be added to the conventional device information transmission
signal, and (ii) information such as "category", "supported frequency
band", and "desired frequency band" may be set to the new item. It is to
be noted that such items are not mandatory and may be omitted.

[0092] As specific examples of Category, "Voice", "Video", "BestEffort",
"Back Ground", and so forth are raised. To the supported frequency band,
information for specifying one or more frequency bands (2.4 GHz band and
5 GHz band) with which the STA2 is capable of performing wireless
communication is set. To the desired frequency band, information for
specifying a frequency band (the 2.4 GHz band or the 5 GHz band) is set,
where the frequency band is desired for use in the wireless communication
with the AP1 by the STA2.

[0093] After obtaining such device information of the STA2, the
device-information-exchange control unit 10 of the AP1 executes a
predetermined key exchange (S103) according to the WPS standard. A key to
be exchanged here is a temporal key for coding and decoding the
connection information distributed in S105, and an actual key for coding
and decoding the wireless signal is included in the connection
information.

[0094] When the predetermined key exchange is completed normally (Yes in
D103), the SSID issuance management unit 7 of the AP1 issues an SSID to
the STA2 and registers the SSID with the connection information
management unit 13 (S104). It is to be noted that the SSID issuance
management unit 7 in the first embodiment assigns a unique SSID to each
of the STA2 to the STA5. Furthermore, the assigned SSID and the
associated device information of the STA2 obtained by the
device-information-exchange control unit 10 are held by the communication
terminal management unit 9.

[0095] Subsequently, the connection information distribution unit 12 of
the AP1 distributes, to the STA2, the connection information for
connecting to the AP1, along with the SSID assigned to the STA2 (S105).
Specifically, the AP1 (i) includes the connection information, including
the SSID, into connection information distribution signal (M8 message)
and (ii) transmits the connection information distribution signal to the
STA2. This method allows to assign a different SSID to each of the STA2
to the STA5.

[0096] Here, the AP1 (i) allocates a channel (operation frequency) in the
5 GHz band or the 2.4 GHz band to the STA2 to the STA5 which are the
sources of the communication start request signal, and (ii) distributes
the connection information associated with the allocated channel.
Specifically, the AP1 allocates the channel based on the supported
frequency information (which is the "supported frequency band", the
"desired frequency band", the "Primary Device Type", and the "category"
described below) received from each of the STA2 to the STA5. A process of
allocating the channel, to be performed by the AP1, is described in
detail below, with reference to FIG. 7A to FIG. 12.

[0097] As a first method of allocation, the AP1 is capable of allocating
the channel based on the "supported frequency band" included in the
device information transmission signal received by each of the STA2 to
the STA5. It is to be noted that the supported frequency band is an item
to which one or more frequency bands are set, where the one or more
frequency bands are the frequency bands in which the wireless
communication terminal is capable of performing wireless communication.
The wireless communication terminal in this embodiment sets all the
frequency bands the wireless communication terminal supports as the
supported frequency bands.

[0098] For example, FIG. 7A shows an example of the supported frequency
band included in the device information transmission signal received from
the STA2 to the STA5. In FIG. 7A, "1" indicates that the frequency band
is supported, and "0" indicates that the frequency band is not supported.
Furthermore, a column enclosed in a thick-frame shows a frequency band to
which the channel allocated to each of the wireless communication
terminals belongs.

[0099] As shown in FIG. 7A, the AP1 allocates the channel in the 5 GHz
band to the STA2 and the STA3 which support both of the 2.4 GHz band and
the 5 GHz band. Furthermore, the AP1 allocates the channel in the 5 GHz
band to the STA4 which only supports the 5 GHz band. Furthermore, the AP1
allocates the channel in the 2.4 GHz band to the STA5 which only supports
the 2.4 GHz band. That is, in the example shown in FIG. 7A, the AP1
allocates (i) the channel in the 5 GHz band to the wireless communication
terminal supporting the 5 GHz band, and (ii) the channel in the 2.4 GHz
band to the wireless communication terminal not supporting the 5 GHz
band.

[0100] Furthermore, as a second method of allocation, the AP1 is capable
of allocating the channel based on the "desired frequency band" included
in the device information transmission signal received by each of the
STA2 to the STA5. It is to be noted that the desired frequency band is an
item to which a frequency band is set, where the frequency band is
desired, by the STA, for use in the wireless communication with the AP1.
The wireless communication terminal in this embodiment may set, as the
desired frequency band, (i) a predetermined frequency band or (ii) a
frequency band which has the best reception state (received power or the
interference state described later).

[0101] For example, FIG. 78 shows an example of the desired frequency band
included in the device information transmission signal received from the
STA2 to the STA5. In FIG. 7B, "1" indicates that the wireless
communication terminal desires to use the frequency band. Furthermore, a
column enclosed in a thick-frame shows a frequency band to which the
channel allocated to each of the wireless communication terminals
belongs.

[0102] As shown in FIG. 7B, the AP1 allocates the channel in the 5 GHz
band to the STA2 to the STA4 which desire the 5 GHz band. Meanwhile, the
AP1 allocates the channel in the 2.4 GHz band to the STA5 which desires
the 2.4 GHz band. That is, in the example in FIG. 7B, the AP1 allocates
the channel of the frequency band desired by the wireless communication
terminal.

[0103] Furthermore, as a third method of allocation, the AP1 is capable of
allocating the channel based on the "Primary Device Type" (a combination
of the Category and the Sub category in FIG. 6) included in the device
information transmission signal received from each of the STA2 to the
STA5. In this case, the AP1 needs to hold a conversion table as shown in
FIG. 8A in advance. This conversion table may be held in a fixed manner
or in a manner that can be changed by the user. The conversion table
shown in FIG. 8A holds (i) the Primary Device Type of a wireless
communication terminal and (ii) a frequency band of the channel to be
allocated to the wireless communication terminal having the Primary
Device Type, such that the Primary Device Type and the frequency band are
associated with each other.

[0104] As shown in FIG. 8B, the AP1 allocates the channel in the 2.4 GHz
band to the STA2 having "Computer" as the Category and "PC" as the Sub
category. In the same manner, the AP1 (i) obtains the frequency band
associated with the Primary Device Type of the STA3 to the STA5 from the
conversion table shown in FIG. 8A and (ii) allocates the channel in the
obtained frequency band to each of the STA3 to the STA5.

[0105] Furthermore, as a fourth method of allocation, the AP1 is capable
of allocating the channel based on the "Category" included in the device
information transmission signal received by each of the STA2 to the STA5.
In this case, the AP1 needs to hold a conversion table as shown in FIG.
9A in advance. The conversion table shown in FIG. 9A holds (i) the
Category of a wireless communication terminal and (ii) the frequency band
of the channel to be allocated to the wireless communication terminal,
such that the Category and the frequency band are associated with each
other. This conversion table may be held in a fixed manner or in a manner
that can be changed by the user.

[0106] As shown in FIG. 9B, the AP1 allocates the channel in the 2.4 GHz
band to the STA2 having "Best Effort" as the category. In the same
manner, the AP1 (i) obtains the frequency band associated with the
category of the STA3 to the STA5 from the conversion table shown in FIG.
9A and (ii) allocates the channel in the obtained frequency band to each
of the STA3 to the STA5.

[0107] Furthermore, as a modification example of the first method of
allocation, the AP1 may obtain the supported frequency band of each of
the wireless communication terminals from the communication start request
signal. A method of obtaining the supported frequency band of the STA2 to
the STA5 from the communication start request signal is described with
reference to FIG. 10A and FIG. 10B.

[0108] As described above, the STA2 transmits the communication start
request signal to all of the channels in the frequency bands which the
STA2 supports. Furthermore, an identical MAC address (MAC-A) is set in
all of the communication start request signals transmitted by the STA2.
The same goes for the STA3 to the STA5.

[0109] As shown in FIG. 10A and FIG. 10B, the AP1 determines that the STA2
supports both of the 2.4 GHz band and the 5 GHz band, upon receipt of the
communication start request signal having the MAC-A set as the MAC
address in both of the 2.4 GHz band and the 5 GHz band. The same goes for
the STA3 and the STA4. Meanwhile, the AP1 determines that the STA5
supports only the 2.4 GHz band, upon receipt of the communication start
request signal having the MAC-D set as the MAC address in the 2.4 GHz
band only.

[0110] As described above, by knowing the supported frequency band of each
of the wireless communication terminal using the communication start
request signal, an advantageous effect is achieved that there is no need
to add a new item to the device information transmission signal as
described in the first method of allocation.

[0111] Furthermore, in addition to the modification example of the first
method of allocation, the AP1 may allocate the channel by taking
magnitude of the received power of the communication start request signal
into consideration. It is to be noted that a "received power (dBm)"
indicates a value measurable by the wireless communication interface 11
of the AP1, and includes, for example, Receive Signal Strength Indication
(RSSI).

[0112] Specifically, as shown in FIG. 11, the AP1 measures the received
power of the communication start request signal received from each of the
STA2 to STA5, in a channel in each frequency band that the AP1 is
operating. It is to be noted that the received power needs to be
independently measured for all of the communication start request
signals, because the RSSI fluctuates according to a positional
relationship between the AP1 and each of the wireless communication
terminals. In FIG. 11, "1" indicates that a communication start request
signal is received in the frequency band. Furthermore, a column enclosed
in a thick-frame shows the frequency band to which the channel allocated
to each of the wireless communication terminals belongs.

[0113] The AP1 allocates a channel in the frequency band having the
highest received power, to the wireless communication terminal which
supports frequency bands. That is, as shown in FIG. 11, the AP1 allocates
a channel in the 5 GHz band having the higher received power, to the STA2
which supports both of the 2.4 GHz band and the 5 GHz band. In the same
manner, the AP1 allocates a channel in the 2.4 GHz band having the higher
received power, to the STA3 which supports both of the 2.4 GHz band and
the 5 GHz band. Meanwhile, the AP1 allocates, to the STA4 and the STA5
which support only one of the 2.4 GHz band and the 5 GHz band, the
channel in the supported frequency band, regardless of the magnitude of
the received power.

[0114] As described above, by allocating the channel in the frequency band
having the higher received power, out of the supported frequency bands,
it is possible to select the appropriate frequency band depending on a
communication environment. It is to be noted that an example which is a
combination of (i) the modification example of the first method of
allocation and (ii) the received power has been described here, however,
without being limited to this example, the same effect may be produced by
combining the received power with the first method of allocation, the
third method of allocation, or the fourth method of allocation.

[0115] Furthermore, in addition to the modification example of the first
method of allocation, the AP1 may allocate a channel by taking the
interference state of each of the frequency bands into consideration. It
is to be noted that the "interference state" indicates a value measurable
by the wireless communication interface 11 of the AP1, and is measurable,
for example, by Packet Error Ratio (PER) of a signal (packet) received in
a channel in each frequency band that the AP1 is operating. Furthermore,
the PER may be calculated based on, for example, a glitch, a Cyclic
Redundancy Check (CRC) of a Physical Layer Convergence Protocol (PLCP)
header, or the like.

[0116] Specifically, as shown in FIG. 12, the AP1 receives the
communication start request signal from each of the STA2 to the STA5 and
measures the interference state of each of the frequency bands. That is,
the AP1 determines that the interference state is bad (in a state where
there are frequent occurrences of interference and indicated as "High" in
FIG. 12), when the PER of the packet received in the 2.4 GHz band is
equal to or more than a predetermined threshold. Meanwhile, the AP1
determines that the interference state is good (in a state where there
are a few occurrences of interference and indicated as "Low" in FIG. 12),
when the PER of a packet received in the 5 GHz band is below the
predetermined threshold. It is to be noted that it is sufficient to
measure the interference state based on a given signal transmitted in
each of the frequency bands, which is different from the case with the
received power described above. Furthermore, the threshold for each of
the frequency bands may be identical or may be set individually for each
of the frequency bands.

[0117] The AP1 allocates the channel in the frequency band with the
interference state lower than the threshold, to the wireless
communication terminal which supports frequency bands. That is, as shown
in FIG. 12, the AP1 allocates the channel in the 5 GHz band with the
interference state lower than the threshold, to the STA2 and the STA3
which support both of the 2.4 GHz band and the 5 GHz band. Meanwhile, the
AP1 allocates, to the STA4 and the STA5 which support only one of the 2.4
GHz band and the 5 GHz band, the channel in the supported frequency band,
regardless of the interference state.

[0118] As described above, by allocating the channel in the frequency band
with the lower interference state, it is possible to select the channel
in the appropriate frequency band depending on the communication
environment. It is to be noted that an example which is a combination of
(i) the modification example of the first method of allocation and the
(ii) interference state has been described here, however, without being
limited to this example, the same effect may be produced by combining the
interference state with the first method of allocation, the third method
of allocation, or the fourth method of allocation. Moreover, the received
power and the interference state may be combined.

[0119] When all of the STA2 to the STA5 shown in FIG. 1 are connected to
the AP1, the communication terminal information managed by the
communication terminal management unit 9 of the AP1 is, for example, as
shown in FIG. 13. It is to be noted that the "MAC" shown in FIG. 13 is
information for identifying each of the STA2 to the STA5 and, for
example, a MAC address may be used. The "Primary Device Type" is
information included in the device information obtained from the STA2 to
the STA5 (the Sub Category, in FIG. 6 in this example), and indicates a
type (Television, PVR, PC, etc.) of each of the STA2 to the STA5. The
"Category" indicates the real-timeliness (Video, BestEffort, etc.)
required for the wireless communication in an application executed by
each of the STA2 to the STA5. The "SSID" indicates the SSID issued by the
SSID issuance management unit 7 to each of the STA2 to the STA5. The
"Band" indicates the frequency band (the 5 GHz band or the 2.4 GHz band)
currently being used for the wireless communication with each of the STA2
to the STA5. The "Channel" indicates the channel currently being used for
the wireless communication with each of the STA2 to the STA5. In FIG. 13,
"36" indicates the channel 36 and "1" indicates the channel 1.

[0120] The "5 GHzFlg" indicates whether or not each of the STA2 to the
STA5 has experienced the wireless communication with the AP1 in the 5 GHz
band (experienced: 1 and unexperienced: 0). The "OldBand" indicates the
frequency band that has been used immediately before the frequency band
indicated in the "Band". It is to be noted that FIG. 13 shows a state
immediately after the STA2 to the STA5 are connected with the AP1, thus
the "OldBand" is not registered.

[0121] As shown in FIG. 13, in the communication terminal to management
unit 9, the following are registered as the communication terminal
information of the STA2: "MAC-A" as the MAC; "Television" as the Primary
Device Type; "Video" as the Category; "SSID-A" as the SSID; "5 GHz" as
the Band; "36" as the Channel; "1" as the 5 GHzFlg; and "-
(unregistered)" as the "Old band".

[0122] Furthermore, in the communication terminal management unit 9, the
following are registered as the communication terminal information of the
STA3: "MAC-B" as the MAC; "PVR" as the Primary Device Type; "Video" as
the Category; "SSID-B" as the SSID; "5 GHz" as the Band; "36" as the
Channel; "1" as the 5 GHzFlg, and "-" as the "Oldband".

[0123] Furthermore, in the communication terminal management unit 9, the
following are registered as the communication terminal information of the
STA4: "MAC-C" as the MAC; "PC" as the Primary Device Type; "BestEffort"
as the Category; "SSID-C" as the SSID; "5GHz" as the Band; "36" as the
Channel; "1" as the 5 GHzFlg; and "-" as the "Oldband".

[0124] Furthermore, in the communication terminal management unit 9, the
following are registered as the communication terminal information of the
STA5: "MAC-D" as the MAC; "PVR" as the Primary Device Type; "Video" as
the Category; "SSID-D" as the SSID; "2.4 GHz" as the Band; "1" as the
Channel; "0" as the 5 GHzFlg; and "-" as the "Oldband". It is to be noted
that the operation frequency of the STA5 is the 2.4 GHz band, since the
STA5 does not support the 5 GHz band.

[0125] It is to be noted that the AP1 determines the real-timeliness
required for the wireless communication in the application executed by
each of the STA2 to the STA5, by referring to the Primary Device Type or
the Category shown in FIG. 13. It is to be noted that both of the Primary
Device Type and the Category are information which indicate a type of the
wireless communication terminal.

[0126] For example, the AP1 determines that the application to be executed
by the STA2, the STA3, and the STA5, all of which are having the
"Television" or the "PVR" as the device information, requires the higher
real-timeliness in the wireless communication than the STA4 that belongs
to "PC". For example, in the conversion table shown in FIG. 8A, it is
possible for the AP1 to determine that the application executed by the
wireless communication terminal having the device information associated
with the 5 GHz band requires the higher real-timeliness in the wireless
communication than the application executed by the wireless communication
terminal having the device information associated with the 2.4 GHz band.

[0127] Furthermore, the AP1 determines that the application executed by
the STA2, the STA3 and the STA5, all of which belong to the "Video"
category requires the higher real-timeliness in the wireless
communication than the application executed by the STA4 which belongs to
the "BestEffort" category. For example, in the conversion table shown in
FIG. 9A, it is possible for the AP1 to determine that the application to
be executed by the wireless communication terminal having the category
associated with the 5 GHz band requires the higher real-timeliness in the
wireless communication than the application to be executed by the
wireless communication terminal having the category associated with the
2.4 GHz band.

[0128] It goes without saying that the Primary Device Type and the
Category are not limited to the above examples and may be any
identification information. Moreover, regarding the Category, the AP1 may
uniquely categorize the wireless communication terminals based on the
Primary Device Type or the like from the STA2. For example, when the
Primary Device Type (the Sub Category in FIG. 6) obtained from the STA2
is the "Television" or the "PVR", in which the application requiring
real-timeliness is often executed, the AP1 may determine that the
Category of the STA2 is "Video". The category here is according to an
access category (Voice, Video, BestEffort, and BackGround) stipulated by
WiFi, however, it goes without saying that other categories may be used.

[0129] Next, an operation of the AP1 when the operation frequency of each
of the STA2 to the STA5 is moved is described using the flowchart in FIG.
14. It is assumed here that, for example, the STA2 starts VoD viewing
from the Internet.

[0130] The communication-terminal-status determination unit 6 of the AP1
always supervises, as an object to be detected, the communication traffic
volume of the STA2, the STA3 and the STA5, all of which belong to the
Video category, out of the STA2 to the STA5 managed by the communication
terminal management unit 9. Specifically, the
communication-terminal-status determination unit 6 detects the
communication traffic volume of a frame having a source MAC address or a
destination MAC address to which one of the "MAC-A", "MAC-B", or "MAC-C"
is set, out of frames received by the AP1.

[0131] When the STA2 starts the VoD, the communication-terminal-status
determination unit 6 of the AP1 detects, for example, that the STA2 is
performing communication at a velocity greater than 5 Mbps (the
threshold) (S201). Here, the following steps are described based on an
assumption that the STA has started the communication greater than 5
Mbps. It is to be noted that to perform communication with a velocity (or
a communication traffic volume) greater than the threshold is an example
of the communication status to satisfy the predetermined condition.

[0132] It is to be noted that although the threshold has been set to 5
Mbps in S201, a specific value is not limited to this value and an
appropriate value may be set depending on such as a type of an
application to be executed. Furthermore, it goes without saying that this
threshold may be the velocity or the communication traffic volume, as
long as the threshold allows the communication-terminal-status
determination unit 6 to determine that the STA2 is executing the
application.

[0133] Next, the communication-terminal-status determination unit 6
determines whether or not the communication is performed in the 5 GHz
band (S202). When the communication is performed in the 5 GHz band (Yes
in S202), the communication-terminal-status determination unit 6 of the
AP1 instructs the frequency control unit 8 to move the STA3 and the STA4
to which the 5 GHz band are allocated other than the STA2, out of the
STA3 to the STA5, to the 2.4 GHz band, based on the communication
terminal information held by the communication terminal management unit
9. More specifically, the communication-terminal-status determination
unit 6 causes the frequency control unit 8 to move the operation
frequencies of the STA3 and the STA4 to which different SSIDs from the
SSID assigned to the STA2 (SSID-A) are assigned, out of the STA2 to the
STA4 performing the wireless communication using the 5 GHz band, to the
2.4 GHz band.

[0134] It is to be noted that the new frequency band in which the STA3 and
the STA4 operate is designated here, however, the channel may be
determined arbitrarily. For example, a vacant channel or a channel being
used by the STA5 that is already in connection may also be designated.

[0135] Then, the communication terminal information managed by the
communication terminal management unit 9 is updated as shown in FIG. 15.
In the case of the first embodiment, specifically, the Band in the
communication terminal information of (i) the STA3 to which the SSID-B,
different from the SSID-A, is assigned and is operating in the 5 GHz band
and (ii) the STA4 to which the SSID-C, different from the SSID-A, is
assigned and is operating in the 5 GHz band, are changed from the 5 GHz
band to the 2.4 GHz band. In this case, the STA3 and the STA4 are
allocated with the same channel as the STA5 to use in the 2.4 GHz band,
and thus the Channel in the communication terminal information is to be
changed from "36" to "1".

[0136] When referring to FIG. 15, regarding the communication terminal
information of the STA2 managed by the communication terminal management
unit 9, the OldBand is updated from "-" to "5 GHz". Furthermore,
regarding the communication terminal information of the STA3 managed by
the communication terminal management unit 9, the Band is updated from "5
GHz" to "2.4 GHz", the Channel is updated from "36" to "1", and the
OldBand is updated from "-" to "5 GHz". Furthermore, regarding the
communication terminal information of the STA4 managed by the
communication terminal management unit 9, the Band is updated from "5
GHz" to "2.4 GHz", the Channel is updated from "36" to "1", and the
OldBand is updated from "-" to "5 GHz". Moreover, regarding the
communication terminal information of the STA5 managed by the
communication terminal management unit 9, the OldBand is updated from "-"
to "2.4 GHz".

[0137] When the value of the Band associated with the SSID-B and the value
of the Band associated with the SSID-C the SSID-C, held by the
communication terminal management unit 9, are changed, the wireless
communication interface 11 transmits the beacon signal including the
SSID-B and the beacon signal including the SSID-C using the new frequency
band (that is, the 2.4 GHz band).

[0138] Meanwhile, after this, the STA3 becomes unable to receive the
beacon signal including the SSID assigned to the STA3, and the STA4
becomes unable to receive the beacon signal including the SSID assigned
to the STA4, even when the beacon signals are supervised in the 5 GHz
band. Therefore, the STA3 and the STA4 start the roaming. By the roaming,
the STA3 becomes able to detect the beacon signal including the SSID of
the STA3, and the STA4 becomes able to detect the beacon signal including
the SSID of the STA4, in the 2.4 GHz band, and thus the STA3 and the STA4
are reconnected to the AP1 in the 2.4 GHz band.

[0139] With the above procedure performed by the AP1, when the STA2
executes the application requiring real-timeliness, the STA3 and the STA4
that are not executing the applications or the STA5 that is executing the
application not requiring real-timeliness are moved to the 2.4 GHz band.
As a result, the STA2 is allowed to execute the application without the
band being overwhelmed.

[0140] Next, in order to describe the operation after S204, a case is
assumed that the STA3 that has been moved to the 2.4 GHz band has
executed the application requiring real-timeliness, as shown in FIG. 15.

[0141] The communication-terminal-status determination unit 6 determines,
when detecting that the STA3 in the Video category is performing wireless
communication at the velocity greater than 5 M bps (Yes in S201), whether
or not the STA3 is operating in the 5 GHz band and whether or not the
STA3 is performing the wireless communication using the 2.4 GHz band
(S202). In this example, the STA3 is performing the wireless
communication using the 2.4 GHz band (Yes in S202).

[0142] Next, the frequency control unit 8 of the AP1 checks the 5 GHzFIg
of the STA3 and checks whether or not there is a history of the STA3
connected to the AP1 in the 5 GHz band (S204). The frequency control unit
8 determines that the STA3 has a function to connect to the 5 GHz band
(Yes in S204), because the STA3 has the history of connection to the AP1
in the 5 GHz band (has the Fig indicating 1). The frequency control unit
8 then changes the operation frequency allocated to the STA3 from the 2.4
GHz band to the 5 GHz band (S205).

[0143] Next, the frequency control unit 8 of the AP1 moves the STA2, which
is performing the wireless communication using the 5 GHz band and to
which the SSID different from the SSID assigned to the STA3 (SSID-6) is
assigned, to the 2.4 GHz band (S203). The specific content of the process
is omitted since it is already described.

[0144] Here, the frequency control unit 8 may further (i) cause the
communication-terminal-status determination unit 6 to determine the
communication status of the STA2, and (ii) determine whether or not to
move the STA2 from the 5 GHz band to the 2.4 GHz band. For example, the
frequency control unit 8 may determine not to move the STA2 to the 2.4
GHz band, when the STA2 is continuously executing the application
requiring real-timeliness (that is, the STA2 is performing the wireless
communication at the velocity greater than 5 Mbps).

[0145] The above structure allows to prevent processes of other wireless
communication terminals, each of which is executing the application
requiring real-timeliness, from being interrupted due to the start of the
execution of the application requiring real-timeliness by a single
wireless communication terminal.

[0146] Meanwhile, when there is no history of the STA3 connected in the 5
GHz band (No in S204), the frequency control unit 8 determines that the
STA3 does not have the function to connect in the 5 GHz band and does not
move the SSID. Alternatively, the frequency control unit 8 may skip the
process of S204 and try to communicate in the 5 GHz band regardless of
the value of the 5 GHzFIg. This allows the frequency control unit 8 to
move, to the 5 GHz band, the wireless communication terminal which has
the function to perform the wireless communication in the 5 GHz band but
has no experience in actual communication in the 5 GHz band.

[0147] Furthermore, in the first embodiment, when the
communication-terminal-status determination unit 6 detects that the
packet communication traffic volume of the STA2 is changed from the
status greater than the threshold to the status equal to or less than the
threshold, the frequency control unit 8 may move the operation
frequencies of the SSID-B and the SSID-C, for which the frequency bands
have been moved, back to the 5 GHz band.

[0148] The above procedure allows even the STA3 and the STA4, for which
the frequency bands have been moved to the 2.4 GHz band, to be moved back
to the 5 GHz band when the STA3 and the STA4 execute the application
requiring real-timeliness. Therefore, the application can be executed
with less effect of the interference. Furthermore, the above process can
be achieved by implementing this function to only the AP1 side, because
the roaming function of the STA2 to the STA4 is used. This allows an easy
relocation from an existing apparatus to the AP1.

Second Embodiment

[0149] Next, the second embodiment is described. The difference between
the first embodiment and the second embodiment is in the way the AP1
assigns the SSID. Specifically, it is different that, in the first
embodiment, the SSID issuance control unit 7 assigns the unique SSID to
each of the STA2 to the STA5, while, in the second embodiment, the SSID
issuance control unit 7 assigns a unique SSID to each of the categories
to which each of the STA2 to the STA5 belongs. The description on
commonalities with the first embodiment is omitted in the description
below to focus on differences.

[0150] The AP1 starts the WPS and so forth with the STA2 (S101), and
obtains the device information of the STA2 (S102), in the same manner as
the first embodiment. The device information includes, for example, the
uuid, the Primary Device Type, or the Category which are assigned
uniquely to each of the STA2 to the STA5.

[0151] For example, as examples of the Primary Device Type, "Television",
"PVR", and "PC" are raised. Specific examples of the category are
"Video", "BestEffort", or the like. It goes without saying that any
identification information may be used in the Primary Device Type and the
Category.

[0152] Moreover, regarding the Category, the AP1 may uniquely categorize
the wireless communication terminals based on the information from the
STA2. For example, when the Primary Device Type of the STA2 is the
"Television" or the "PVR", in which the application requiring
real-timeliness is often executed, the AP1 may determine that the
category of the STA2 is the "Video". It goes without saying that the
category here is according to an access category (Voice, Video,
BestEffort, and BackGround) stipulated by WiFi, however, other category
may be used.

[0153] After obtaining such device information of the STA2, a key exchange
according to the WPS standard is executed (S103). When the predetermined
key exchange is completed, the SSID issuance management unit 7 of the AP1
issues an SSID different for each of the categories to the STA2, and
registers the SSID with the connection information management unit 13
(S104). Then, the SSID issuance management unit 7 distributes the
connection information to the STA2, the connection information being for
connecting with the AP1 (S105). This method allows to assign a different
SSID to each of the categories.

[0154] Specifically, it is different that the issuance control unit 7
assigns, in the first embodiment, the SSID unique to each of the STA2 to
the STA5, while, the SSID unique to each of the categories to which each
of the STA2 to the STA5 belongs, in the second embodiment. Other
processes shown in FIG. 3 (S101 to S103 and S105) are common with the
first embodiment.

[0155] When all of the STA2 to the STA5 shown in FIG. 1 are connected to
the AP1, the communication terminal information managed by the
communication terminal management unit 9 of the AP1 is as shown in FIG.
16.

[0156] As shown in FIG. 16, in the communication terminal management unit
9, the following are registered as the communication terminal information
of the STA2: "MAC-A" as the MAC; "Television" as the Primary Device Type;
"Video" as the Category; "SSID-A" as the SSID; "5 GHz" as the Band; "1"
as the 5 GHzFlg; and "-" as the Oldband.

[0157] Furthermore, in the communication terminal management unit 9, the
following are registered as the communication terminal information of the
STA3: "MAC-B" as the MAC, "PVR" as the Primary Device Type, "Video" as
the Category, "SSID-A" as the SSID, "5 GHz" as the Band, "36" as the
Channel, "1" as the 5 GHzFlg, and "-" as the Oldband.

[0158] Furthermore, in the communication terminal management unit 9, the
following are registered as the communication terminal information of the
STA4: "MAC-C" as the MAC, "PC" as the Primary Device Type, "BestEffort"
as the Category, "SSID-C" as the SSID, "5 GHz" as the Band, "36" as the
Channel, "1" as the 5 GHzFlg, and "-" as the Oldband.

[0159] Moreover, in the communication terminal management unit 9, the
following are registered as the communication terminal information of the
STA5: "MAC-D" as the MAC, "PVR" as the Primary Device Type, "Video" as
the Category, "SSID-D" as the SSID, "2.4 GHz" as the Band, "1" as the
Channel, "0" as the 5 GHzFlg, and "-" as the Oldband. It is to be noted
that the operation frequency (Band) of the STA5 is the 2.4 GHz band,
because the STA5 does not support the 5 GHz band. Therefore, the Category
of the STA5 is the "Video", however, the STA5 is assigned with not
"SSID-A" which is the same as the STA2 and the STA3 but "SSID-B".

[0160] Next, an operation of the AP1 when the operation frequency is moved
is described using the flowchart in FIG. 17. It is assumed here that, for
example, the STA2 starts VoD viewing from the Internet.

[0161] The communication-terminal-status determination unit 6 of the AP1
always supervises, as the object to be detected, the communication
traffic volume of the STA2, the STA3 and the STA5 which belong to the
Video category, out of the STA2 to the STA5 managed by the communication
terminal management unit 9 (S301).

[0162] When the STA2 starts the VoD, the communication-terminal-status
determination unit 6 of the AP1 detects, for example, that the STA2 is
performing communication at a velocity greater than 5 Mbps (the
threshold) (Yes in S301). It goes without saying that this threshold may
be the velocity or the communication traffic volume, as long as it allows
the communication-terminal-status determination unit 6 to determine that
the STA2 is executing the application.

[0163] Next, the communication-terminal-status determination unit 6
determines whether or not the communication is performed in the 5 GHz
band (S302). When the communication is performed in the 5 GHz band (Yes
in S302), the communication-terminal-status determination unit 6 of the
AP1 instructs the frequency control unit 8 to switch the frequency band
to use of the STA4, which belongs to the category different from the
STA2, from the 5 GHz band to the 2.4 GHz band, based on the communication
terminal information of the communication terminal management unit 9. It
is to be noted that the new frequency band is designated here, however,
the channel may be determined arbitrarily. For example, a vacant channel
or a channel being used by the STA5 that is already in connection may be
designated.

[0164] In the second embodiment, specifically, the SSID-C which is
assigned to the STA4 and is operating in the 5 GHz band is changed to
operate in the 2.4 GHz band. That is, the Band associated with the SSID-C
of the STA4 is changed from the "5 GHz band" to the "2.4 GHz band".
Accordingly, the communication terminal information managed by the
communication terminal management unit 9 is updated as shown in FIG. 18.

[0165] When referring to FIG. 18, regarding the communication terminal
information of the STA2 managed by the communication terminal management
unit 9, the Oldband is updated from "-" to "5 GHz band". Furthermore,
regarding the communication terminal information of the STA3 managed by
the communication terminal management unit 9, the OldBand is updated from
"-" to "5 GHz band". Furthermore, regarding the communication terminal
information of the STA4 managed by the communication terminal management
unit 9, the Band is updated from the "5 GHz band" to the "2.4 GHz band",
the Channel is updated from "36" to "1", and the OldBand is updated from
"-" to "5 GHz band". Moreover, regarding the communication terminal
information of the STA5 managed by the communication terminal management
unit 9, the OldBand is updated from "-" to the "2.4 GHz band".

[0166] After this, the STA4 starts the roaming because the STA4 is no
longer capable of receiving the beacon signal including STA-C. Performing
the roaming enables the STA4 to detect the beacon signal including the
SSID-C in the 2.4 GHz band, and thus the STA4 is reconnected to the AP1
in the 2.4 GHz band.

[0167] Furthermore, in the second embodiment, when the
communication-terminal-status determination unit 6 of the AP1 does not
detect a certain amount of packet communication traffic volume any more,
the frequency control unit 8 may move the operation frequency of the
SSID-C, for which the operation frequency has been moved from the "2.4
GHz band", back to the "5 GHz band".

[0168] The above procedure taken by the AP1 allows the STA2, the STA3, and
the STA5, each of which executes the application requiring
real-timeliness, to be divided by categories and thus enables a
compartmentalization of the frequency bands of the wireless LANs. As a
result, an artifact due to the overwhelmed band or a decrease in the
velocity is mitigated. Moreover, the difficulty in introducing the
roaming function of the STA2 to the STA5 is lowered.

Third Embodiment

[0169] The difference between the third embodiment and the first
embodiment is in a specific procedure of determining whether or not the
STA2, the STA3 and the STA5 has executed the application requiring
real-timeliness. Specifically, it is different that the
communication-terminal-status determination unit 6 determines, in the
first embodiment, based on whether or not the volume of the wireless
communication is greater than the threshold, while, in the second
embodiment, based on whether or not priority of communication data is
greater than the threshold. It is to be noted that to perform
communication with priority of communication data greater than the
threshold is an example of the communication status to satisfy the
predetermined condition. The description on commonalities with the first
embodiment is omitted in the description below to focus on differences.

[0170] In the third embodiment, a specific process is described in detail,
where the process is for determining, by the
communication-terminal-status determination unit 6, that the STA2 has
executed the application requiring real-timeliness. Other process
operations by the AP1 are common with the first embodiment.

[0171] As shown in FIG. 20, the communication-terminal-status
determination unit 6 of the AP1 always supervises, as the object to be
detected, the priority of the STA2, STA3 and the STA5 which belong to the
Video category, out of the STA2 to the STA5 managed by the communication
terminal management unit 9.

[0172] An example of the object to be detected is (i) a Type of Service
(ToS) field or (ii) a DSCP field, shown in FIG. 19, each of which
indicates the priority of the IP packet. These are fields which describe
the priority of the IP packet, and the ToS field, for example, describes
eight levels of priority. The priority of a Video stream, stipulated by
WiFi and so forth, is described as 5.

[0173] When the STA2 starts the VoD, the priority is added to a ToS field
of an IP header of a packet, where the packet is set with an IP address
of the STA2 as an destination address. The communication-terminal-status
determination unit 6 detects whether or not the priority is equal to or
more than a certain stipulation (for example, equal to or more than 5)
(S401). Regarding the stipulation for the priority, it goes without
saying that the priority is not necessarily be equal to or more than 5,
as long as it is complying with a system or a standard. Furthermore, it
goes without saying that it is sufficient when it allows the
communication-terminal-status determination unit 6 to determine that the
STA2 is executing the application.

[0174] Then, the frequency control unit 8 performs the same process as in
the first embodiment to change the association between the SSID and the
Band in the communication terminal management unit 9, to (i) cause the
STA2, which has executed the application requiring high real-timeliness,
to operate in the 5 GHz band, and (ii) cause the to STA3 to the STA5,
other than the STA2, to operate in the 2.4 GHz band.

[0175] Furthermore, in the third embodiment, when the
communication-terminal-status determination unit 6 does not detect the
packet of the STA2 added with the priority for a certain period, the
frequency control unit 8 may move the operation frequencies of the SSID-B
and the SSID-C, for which the operation frequencies have been moved, from
the "2.4 GHz band" back to the "5 GHz band".

Fourth Embodiment

[0176] The difference between the fourth embodiment and the second
embodiment is in a specific procedure of determining whether or not the
STA2, the STA3 and the STA5, in the Video category, have executed the
application requiring real-timeliness. Specifically, it is different that
the communication-terminal-status determination unit 6 determines, in the
second embodiment, based on whether or not the volume of the wireless
communication is greater than the threshold, while, in the fourth
embodiment, based on whether or not the priority of the communication
data is greater than the threshold. The description on commonalities with
the second embodiment is omitted in the description below to focus on
differences.

[0177] In the fourth embodiment, a specific process is described in
detail, where the process is for determining, by the
communication-terminal-status determination unit 6, that the STA2 has
executed the application requiring real-timeliness. Other process
operations by the AP1 are common with the second embodiment.

[0178] The communication-terminal-status determination unit 6 of the AP1
always supervises, as the object to be detected, the priority of
communication packets of STA2, the STA3 and the STA5 which belong to the
Video category, out of the STA2 to the STA5 managed by the communication
terminal management unit 9.

[0179] An example of the object to be detected is 1) a Type of Service
(ToS) field or 2) a DSCP field, shown in FIG. 19, each of which indicates
the priority of the IP packet. These are fields which describe the
priority of the IP packet, and the ToS field, for example, describes
eight levels of priority. The priority of the Video stream, stipulated by
WiFi and so forth, is described as 5.

[0180] When the STA2 starts the VoD, the priority is added to the ToS
field of the IP header of the packet, where the packet is set with the IP
address of the STA2 as the destination address. The
communication-terminal-status determination unit 6 detects whether or not
the priority is equal to or more than a certain stipulation (for example,
equal to or more than 5) (S401). Regarding the stipulation for the
priority, it goes without saying that the priority is not necessarily be
equal to or more than 5, as long as it is complying with a system or a
standard. It goes without saying that it is sufficient when it allows the
communication-terminal-status determination unit 6 to determine that the
STA2 is executing the application.

[0181] Then, the frequency control unit 8 performs the same process as in
the first embodiment to changes the association between the SSID and the
Band in the communication terminal management unit 9, to (i) cause the
STA2 that has executed the application requiring high real-timeliness and
the STA3 that belongs to the same category as the STA2, to operate in the
5 GHz band, and (ii) cause the STA4 and the STA5, other than the STA2 and
the STA3, to operate in the 2.4 GHz band.

[0182] Furthermore, in the fourth embodiment, when the
communication-terminal-status determination unit 6 does not detect the
packet of the STA2 added with the priority for a certain period, the
frequency control unit 8 may move the operation frequency of the SSID-C,
for which the operation frequency has been moved, from the "2.4 GHz band"
back to the "5 GHz band".

Fifth Embodiment

[0183] Next, the fifth embodiment is described. First, the structure of
the wireless communication terminal (STA) 2 is described using FIG. 22.
The STA2 in the fifth embodiment includes a wireless communication
interface 14, an application control unit 15, an application
determination unit 16, an application information notification unit 17, a
device-information-exchange control unit 18, and a connection information
management unit 19.

[0184] The wireless communication interface 14 is an interface for
transmitting and receiving a wireless signal between the AP1. That is,
the wireless communication interface 14 transmits, as the wireless
signal, the data generated by the application information notification
unit 17, the device-information-exchange control unit 18, and so forth,
to the AP1. Furthermore, the wireless communication interface 14
generates data from the wireless signal received from the AP1, and
notifies the generated data to the device-information-exchange control
unit 18, or the like. Moreover, the wireless communication interface 11
receives the beacon signal transmitted from the AP1 in a predetermined
time interval.

[0185] The application control unit 15 executes an application requiring
the wireless communication between the AP1. An example of such an
application is an application which performs streaming reproduction of an
image data from a content server and so forth. The application
determination unit 16 determines the real-timeliness in the wireless
communication required for the application to be executed by the
application control unit 15. The application information notification
unit 17 notifies, to the AP1, the result of determination by the
application determination unit 16. Specifically, the application
information notification unit 17 transmits the application execution
notification to the AP1, when the application requiring real-timeliness
in the wireless communication has been started. Meanwhile, the
application information notification unit 17 transmits the application
completion notification to the AP1, when the execution of the application
which has been executed by the application control unit 15 is completed.

[0186] The device-information-exchange control unit 18 exchanges the
device information between the AP1. That is, the
device-information-exchange control unit 18 (i) transmits the device
information of the STA2 to the AP1 and (ii) obtains the device
information of the AP1. The connection information management unit 19
holds information (key information, etc.) required by the wireless
communication terminal for performing wireless communication with the
AP1.

[0187] It is to be noted that, after receiving the application execution
notification from the STA2, the AP1 uses (i) the 5 GHz band for the
wireless communication with the STA2 and (ii) the 2.4 GHz band for the
wireless communication with other STAs, the STA3 to the STA5, each of
which is assigned with the SSID different from the STA2. Meanwhile, after
receiving the application completion notification from the STA2, the AP1
returns the frequency band of the STA that has had the frequency band
switched according to the application execution notification back to the
frequency band used prior to the switching, out of the STA3 to the STA5.

[0188] Next, the operation of the STA2 according to the fifth embodiment
is described, using the flowchart in FIG. 23. In the fifth embodiment, it
is assumed that the STA2 has executed the VoD. Furthermore, the state of
the STA2 connected with the AP1 is the same as in the first embodiment,
and the communication terminal information shown in FIG. 13 is held by
the communication terminal management unit 9 of the AP1.

[0189] The application determination unit 16 of the STA2 determines
whether or not the STA2 is executing the application requiring high
real-timeliness in the wireless communication (for example, a video
viewing using the VoD or DLNA).

[0190] When the application determination unit 16 determines that the high
real-timeliness is required (Yes in S601), the application information
notification unit 17 transmits the application execution notification to
the AP1 (S602). It is to be noted that the way of notification is not
limited. It goes without saying that, for example, the application
execution notification may be included in an Information Elements (IE) of
a MAC frame in the wireless LAN, or may be a packet in an IP layer. It is
sufficient when it is notified to the AP1 that the application has been
executed.

[0191] Next, the operation of the AP1 after receiving the application
execution notification from the STA2 is described, using the flowchart in
FIG. 24.

[0192] When the application execution notification is received from the
STA2 (Yes in S701), the communication-terminal-status determination unit
6 determines whether or not the communication is performed in the 5 GHz
band (S702).

[0193] When the communication is performed in the 5 GHz band (Yes in
S702), the communication-terminal-status determination unit 6 of the AP1
instructs the frequency control unit 8 to move the frequency bands of the
STA3 and the STA4, which belong to the category different from the STA2,
from the "5 GHz band" to the "2.4 GHz band", based on the communication
terminal information in the communication terminal management unit 9. It
is to be noted that the frequency band is designated here, however, the
channel may be determined arbitrarily. For example, a vacant channel or a
channel being used by the STA5 that is already in connection may be
designated.

[0194] In the case of the fifth embodiment, specifically, regarding the
communication terminal information of the STA3 and the STA4, each of
which is currently performing wireless communication using the 5 GHz band
and assigned with the SSID different from the STA2, the Band associated
with the SSID-B and the Band associated with the SSID-C are switched from
the "5 GHz band" to the "2.4 GHz band".

[0195] When the Band associated with the SSID-B and the Band associated
with the SSID-C are changed, the STA3 and the STA4 start the roaming,
because the STA3 becomes unable to receive the beacon signal including
the SSID of the STA3 and the STA4 becomes unable to receive the beacon
signal including the SSID of the STA4, in the 5 GHz band. By performing
the roaming, the STA3 becomes able to detect the beacon signal including
the SSID of the STA3 in the 2.4 GHz band, and the STA4 becomes able to
detect the beacon signal including the SSID of the STA4 in the 2.4 GHz
band, and thus the STA3 and the STA4 are reconnected to the AP1 in the
2.4 GHz band.

[0196] Next, in order to describe the operation after S204, a case is
assumed that the STA3, which has been moved to the 2.4 GHz band, has
executed the application requiring the real-timeliness.

[0197] The communication-terminal-status determination unit 6 receives the
application execution notification from the STA3 (S701). The
communication-terminal-status determination unit 6 determines that the
communication is performed in the 2.4 GHz band in S702 (No in S702).

[0198] Next, the communication-terminal-status determination unit 6 checks
the 5 GHzFIg of the STA3 and checks whether or not the STA3 is connected
in the 5 GHz band. Since the STA3 has the history of connection in the 5
GHz band (has the Fig indicating 1), the communication-terminal-status
determination unit 6 determines that the STA3 has the function to connect
in the 5 GHz band (Yes in S704), and the frequency control unit 8 changes
the operation frequency from the "2.4 GHz band" to the "5 GHz band"
(S705). When the STA3 has no history of connection in the 5 GHz band, the
communication-terminal-status determination unit 6 determines that the
STA3 does not have the function to connect in the 5 GHz band (No in
S704), and the frequency control unit 8 does not change the operation
frequency.

[0199] Furthermore, the fifth embodiment is described based on the first
embodiment, however, the operations after receiving the application
execution notification from the STA2 may be replaced with the operations
in the second embodiment.

[0200] Furthermore, in the fifth embodiment, when the execution of the
application is completed, the STA2 transmits the application completion
notification to the AP1. After receiving the application completion
notification, the AP1 may return the operation frequencies of the STA3
and the STA4 that have had the frequency bands switched upon receiving
the preceding application execution notification to the "5 GHz band" from
the "2.4 GHz band".

[0201] The above procedure allows to implement the switching of the
operation frequencies at appropriate timing, by linking with the
application requiring high real-timeliness in the wireless communication.

Other Modification Examples

[0202] It is to be noted that although the present invention is described
based on aforementioned embodiment, the present invention is obviously
not limited to such embodiment. The following cases are also included in
the present invention.

[0203] Each of the aforementioned apparatuses is, specifically, a computer
system including a microprocessor, a ROM, a RAM, a hard disk unit, a
display unit, a keyboard, a mouse, and the so on. A computer program is
stored in the RAM or hard disk unit. The respective apparatuses achieve
their functions through the microprocessor's operation according to the
computer program. Here, the computer program is configured by combining
plural instruction codes indicating instructions for the computer, in
order to achieve predetermined functions.

[0204] A part or all of the constituent elements constituting the
respective apparatuses may be configured from a single System-LSI
(Large-Scale Integration). The System-LSI is a super-multi-function LSI
manufactured by integrating constituent elements on one chip, and is
specifically a computer system configured by including a microprocessor,
a ROM, a RAM, and so forth. The System-LSI is a super-multi-function LSI
manufactured by integrating constituent elements on one chip, and is
specifically a computer system configured by including a microprocessor,
a ROM, a RAM, and so forth. A computer program is stored in the RAM. The
respective apparatuses achieve their functions through the
microprocessor's operation according to the computer program.

[0205] A part or all of the constituent elements constituting the
respective apparatuses may be configured as an IC card which can be
attached and detached from the respective apparatuses or as a stand-alone
module. The IC card or the module may also include the aforementioned
super-multi-function LSI. The IC card or the module achieves its function
through the microprocessor's operation according to the computer program.
The IC card or the module may also be implemented to be tamper-resistant.

[0206] The present invention may be a method of the above. The present
invention may be a computer program for realizing the previously
illustrated method, using a computer, and may also be a digital signal
including the computer program.

[0207] Furthermore, the present invention may also be realized by storing
the computer program or the digital signal in a computer readable
recording medium such as flexible disc, a hard disk, a CD-ROM, an MO, a
DVD, a DVD-ROM, a DVD-RAM, a BD (Blu-ray Disc), and a semiconductor
memory. Furthermore, the present invention also includes the digital
signal recorded in these recording media.

[0208] Furthermore, the present invention may also be realized by the
transmission of the aforementioned computer program or digital signal via
a telecommunication line, a wireless or wired communication line, a
network represented by the Internet, a data broadcast and so forth.

[0209] The present invention may also be a computer system including a
microprocessor and a memory, in which the memory stores the
aforementioned computer program and the microprocessor operates according
to the computer program.

[0210] Furthermore, by transferring the program or the digital signal by
recording onto the aforementioned recording media, or by transferring the
program or digital signal via the aforementioned network and the like,
execution using another independent computer system is also made
possible.

[0211] The above embodiment and the modification examples may be combined
respectively.

[0212] The embodiment of the present invention has been described with
reference to the diagrams, however, the present invention is not limited
to the embodiment illustrated. It is possible to add, to the embodiment
illustrated, various corrections or modifications along with the full
scope of equivalents to the present invention.

INDUSTRIAL APPLICABILITY

[0213] An access point terminal and a wireless communication terminal
according to the present invention are useful in a wireless LAN network
which switches an operation frequency depending on an application.